Email Triage

I've read a little on the web about various time management techniques such as 43 Folders along with Getting Things Done. The problem I have with a lot of these systems is that they still generate hardcopy detritus - don't we live in a digital age? Maybe they just feel too complicated for me. I tried using the pure task list approach in Outlook, but somehow emails that generated tasks never made it to the task list. These days I triage emails into one of the following:

• Action is for something that I need to do
• Reply is for something that I need to send an email in reply
• Review is for something that I need to read in depth later (like a design document)
• FYI is for something that I need to hold on to, but don't need just yet (like the spec for next weeks meeting)

Each of these is a specific flag colour which I can access from a custom toolbar. I can also mark the email as done when I complete the action. The exception is the email which fits none of these categories and so doesn't get a flag. This means that at the end of the month, I can simply delete all the emails that never got a flag, rather then having to sort through them to identify anything I need to keep. How do you manage your emails?